Sulfonic Acid Functional Groups Research Articles

Evidences for the influence from key chemical structures of per- and polyfluoroalkyl substances on their environmental behaviors

This study carried out the atmospheric and precipitation observation in Beijing for nearly one year, and firstly simultaneously observed the pollution characteristics of PFASs and their main isomers, focusing on their gas-particle partitioning mechanism and dry and wet deposition characteristics. After deducting PFASs in the aqueous phase of particulate matter, the gas-particle partitioning coefficients (−7.04 to −5.49) were about 3–4 units smaller than before (−2.77 to −1.51), and all were smaller than 0, which indicated that each PFAS and isomer were more distributed in the gas phase. Dry deposition was dominant in the atmospheric deposition of each PFAS and isomer with relative contribution of 66 ± 17%, but the relative contribution of dry deposition was significantly different. It was found that the gas-particle partitioning coefficient can be influenced by key chemical structures such as carbon chain length, functional group type, and isomer structure. Furthermore, the gas-particle partitioning can influence the dry and wet deposition of PFASs. Specifically, PFASs with longer carbon chains, carboxylic acid functional group (compared to sulfonic acid functional group) or PFOA branched chain structures had larger gas-particle partitioning coefficients and can be more distributed in the hydrophobic phase of particulate matter, and their relative contributions of dry deposition were smaller.

Proton Transport Functionality-Enabled Carbon Support for Improved Fuel Cell Performance and Durability.

A novel Monarch carbon material with proton conduction capability due to the presence of sulfone/sulfoxide/sulfonic groups on the surface was evaluated as a potential cathode catalyst support to enable an electrode design with low ionomer content in proton exchange membrane (PEM) fuel cells. X-ray photoelectron spectroscopy of the carbon support confirmed the sulfonic acid functionality, while dynamic vapor sorption measurements proved higher water uptake. Electrochemical impedance spectroscopy of the PtCo/Monarch electrodes showed higher proton conductivity than state-of-the-art PtCo/C with decreasing ionomer to carbon (I/C) content due to the presence of sulfonic acid functional groups on the carbon support surface. Fuel cell performance and durability measurements showed better high-current density performance for PtCo/Monarch with a 75% lower ionomer content in the electrode compared to that of PtCo/C. Our studies indicate that Monarch carbon could be a viable alternative support for PEM fuel cell catalyst applications.

The Effect of Organic Acid Dopants on the Specific Capacitance of Electrodeposited Polypyrrole-Carbon Nanotube/Polyimide Composite Electrodes

Energy storage materials are constantly being improved and developed to cope with the ever-increasing demand of the electronic devices industry. Various synthetic approaches have been used to manufacture electrode materials. This paper is focused on the use of intrinsically conductive polymers such as polypyrrole (PPy) in the development of single-walled carbon nanotube-polyimide, SWCNT-PI, supercapacitor electrode materials. The polypyrrole used in the study is doped with different organic acid dopants of various sizes, including styrene sulfonic acid, SSA, toluene sulfonic acid, TSA, dodecylbenzene sulfonic acid, DBSA, naphthalene disulfonic acid, NDSA, and naphthalene trisulfonic acid, NTSA. The number of sulfonic acid functional group per dopant molecule varied from one to three, while the number of benzene rings in the aromatic unit varied from one to two. It is believed that, as the sulfonic acid to the dopant molecule ratio changes, the morphology and electrochemical properties of the doped PPy-coated electrode material will change accordingly. The change in the morphology of the doped PPy, due to the respective dopant, is correlated with the change in the electrochemical properties of the modified composite electrode. The naphthalene trisulfonic acid (NTSA) dopant was found to produce the highest specific capacitance of about 119 F/g at 5 mV/s. Furthermore, the NTSA-doped PPy electrode system showed the highest porosity and highest tan delta damping peak height for the a-transition. The styrene sulfonic acid-doped PPy/SWCNT-PI electrode material showed an impressive storage modulus of more than 2 GPa, but lower porosity. Styrene polymerization is believed to have occurred. The results obtained indicate that the porosity and electrochemical properties of the electrode materials are correlated.

Polyethylene glycol-based halogen-free acidic deep eutectic solvents for removal of olefins from aromatics

In this study, seven novel green acidic deep eutectic solvents (ADESs) based on polyethylene glycol (PEG) was successfully synthesized. Organic acids containing carboxylic acid and sulfonic acid functional groups were utilized as hydrogen bond donors (HBDs) for the synthesis. The formation mechanism of ADESs was elucidated through 1H NMR and FTIR spectroscopy, as well as density functional theory (DFT) calculations. Acetonitrile-IR spectroscopy was employed to investigate the acidity of the prepared ADESs, revealing the superior Lewis acidity of ADESs derived from carboxylic acid functional groups. The generation of Lewis acidic sites can be attributed to the hydrogen bonding interaction between the hydroxyl groups of PEG and the carboxylic acid functional groups, promoting the dissociation of carboxylic acid molecules. The obtained DES [PEG:2FA] and [PEG:2AA], with formic acid (FA) and acetic acid (AA) as HBDs, exhibited remarkable efficiency in removing olefins from aromatics under mild reaction conditions. GC–MS analysis of the reaction products confirmed the formation of alkylbenzenes, indicating the occurrence of alkylation reactions. Furthermore, a rational reaction mechanism was proposed to elucidate the reaction process of aromatics and olefins on acidic sites.

Fabrication of a magnetic metal-organic framework/covalent organic framework composite for simultaneous magnetic solid-phase extraction of seventeen trace quinolones residues in meats

Effective capture of quinolones (QNs) in animal-derived food is a vital procedure for food safety monitoring. However, the lack of adsorption specificity and difficult to recycle in complex substrate conditions have been major problems for most of the adsorbents. In this work, a magnetic Fe3O4/MOF/COF composite (named Fe3O4@NH2−MIL-125@TpPa-SO3H) was successfully synthesized with good magnetic responsiveness and conspicuous affinity towards QNs. The Fe3O4/MOF/COF composite was used as a magnetic solid-phase extraction (MSPE) adsorbent for pretreatment and determination of QNs in meat samples. Under optimal MSPE conditions in combination with high performance liquid chromatography-quadrupole orbitrap high resolution mass spectrometer (HPLC-Q-Orbitrap HRMS), the proposed method had good linearity (R2 ≥ 0.9978) from 0.01 to 100ng g−1, low limits of detection (0.0016 to 0.0940ng g−1), good precision with relative standard deviations lower than 5.8%. This method was effectively applied to the detection of 17 QNs in the spiked pork, chicken and beef samples with satisfactory recoveries from 83.9 to 106.2%. The separation selectivity mainly due to the π–π interaction, hydrogen bonding, and electrostatic attraction between QNs and the sulfonic acid and amino functional groups of the composite. After verification, the stability and reusability of the composite meet the requirements of complex matrix sample pretreatment. The developed MSPE method based on the magnetic Fe3O4/MOF/COF composite provided an ideal sample pretreatment alternative for determining trace QNs in complex matrixes with selectivity, simplicity, rapidity, and efficiency.

Evaluation of water desalination performances of functionalized nanoporous graphene membranes by molecular dynamics simulation

Nanoporous graphene membrane (NPGM) is a promising candidate for water desalination due to its unique features, such as chemical stability, high resistance to chlorine and fouling, excellent mechanical strength, and tunable permeability. In this work, the water desalination performances of small- and large-pore, pristine and functionalized NPGMs, with the latter containing amide, sulfonic acid, thiourea, and carbamate functional groups, were evaluated by molecular dynamics (MD) simulation. Our results indicate that pore functionalization leads to a decrease in water flow rate through the membrane. Among functionalized NPGMs, large-pore, amide-functionalized NPGM exhibited the highest water flow rate. In terms of ion rejection performance, pore functionalization resulted in partial Na+ and Cl− ion rejection by both small- and large-pore NPGMs. For small-pore, functionalized NPGMs, the rejection of Na+ and Cl− ions were higher than 98%. Comparing between the ion rejection performances of large-pore, functionalized NPGMs, the following order of Na+ ion rejection rates were observed: carbamate > sulfonic acid > thiourea > amide. The carbamate functionalization of large-pore NPGM led to about 21% and 18% Na+ and Cl− rejection, respectively. This observation is in good correlation with the smallest effective pore diameter in the carbamate-functionalized NPGM and the largest ion-carbamate interaction energies.

Potential Alzheimer's disease therapeutic nano-platform: Discovery of amyloid-beta plaque disaggregating agent and brain-targeted delivery system using porous silicon nanoparticles.

There has been a lot of basic and clinical research on Alzheimer's disease (AD) over the last 100 years, but its mechanisms and treatments have not been fully clarified. Despite some controversies, the amyloid-beta hypothesis is one of the most widely accepted causes of AD. In this study, we disclose a new amyloid-beta plaque disaggregating agent and an AD brain-targeted delivery system using porous silicon nanoparticles (pSiNPs) as a therapeutic nano-platform to overcome AD. We hypothesized that the negatively charged sulfonic acid functional group could disaggregate plaques and construct a chemical library. As a result of the in vitro assay of amyloid plaques and library screening, we confirmed that 6-amino-2-naphthalenesulfonic acid (ANA) showed the highest efficacy for plaque disaggregation as a hit compound. To confirm the targeted delivery of ANA to the AD brain, a nano-platform was created using porous silicon nanoparticles (pSiNPs) with ANA loaded into the pore of pSiNPs and biotin-polyethylene glycol (PEG) surface functionalization. The resulting nano-formulation, named Biotin-CaCl2-ANA-pSiNPs (BCAP), delivered a large amount of ANA to the AD brain and ameliorated memory impairment of the AD mouse model through the disaggregation of amyloid plaques in the brain. This study presents a new bioactive small molecule for amyloid plaque disaggregation and its promising therapeutic nano-platform for AD brain-targeted delivery.

Factors affecting mixed-mode retention properties of cation-exchange stationary phases

Cation-exchange stationary phases were characterized in different chromatographic modes (HILIC, RPLC, IC) and applied to the separation of non-charged hydrophobic and hydrophilic analytes. The set of columns under investigation included both commercially available cation-exchangers and self-prepared PS/DVB-based columns, the latter consisting of adjustable amounts of carboxylic and sulfonic acid functional groups. The influence of cation-exchange site and polymer substrate on the multimodal properties of cation-exchangers was identified using selectivity parameters, polymer imaging and excess adsorption isotherms. Introducing weakly acidic cation-exchange functional groups to the unmodified PS/DVB-substrate effectively reduced hydrophobic interactions, whilst a low degree of sulfonation (0.09 to 0.27% w/w sulphur) mainly influenced electrostatic interactions. Silica substrate was found to be another important factor for inducing hydrophilic interactions. The presented results demonstrate that cation-exchange resins are suitable for mixed-mode applications and offer versatile selectivity.

Sulfonated poly(ether ether ketone) membranes for vanadium redox flow battery enabled by the incorporation of ionic liquid‐covalent organic framework complex

AbstractIn vanadium redox flow battery (VRFB). Sulfonated poly(ether ether ketone) (SPEEK) is viewed as a promising alternative to Nafion as a material for vanadium liquid flow battery membrane, due to its low cost and high proton conductivity. However, SPEEK membranes have a Trade‐Off effect of proton conduction and ion selectivity, which limits the performance of VRFB. Here, we exploited the Donnan effect of imidazole cations in ionic liquids (ILs) to improve the ion selectivity of SPEEK membrane. In addition, used porous covalent organic framework materials (COF) with sulfonic acid functional groups to immobilize ionic liquids, which reduced the loss of ILs. The ion selectivity of the SPEEK membrane was further improved. As a result, the cell performance of the composite membrane is improved. At a constant current density of 40 mA cm−2, SPEEK/IL‐5@TpPa‐SO3H‐3 membrane exhibits high coulombic efficiencies (CE: 98.43%) and energy efficiencies (EE: 91.7%). Furthermore, the energy efficiency of the SPEEK/IL‐5@TpPa‐SO3H‐3 membrane decreases only 2.1% after 60 charge/discharge cycles at 100 mA cm−2. Our work proposed a cost‐effective, high‐performance membrane for VRFB.

Stable isotope labeling for detection of ozonation byproducts in effluent organic matter with FT-ICR-MS

Despite effluent organic matter (EfOM) being a major consumer of ozone during wastewater treatment, little is known about ozonation byproducts (OBPs) produced from EfOM. To unambiguously identify OBPs, heavy ozone was used to ozonate EfOM, resulting in 18O labeled and unlabeled OBPs. Labeled OBPs mostly represent a single 18O transfer and were classified as either direct or indirect OBPs based on the 18O/16O intensity ratios of the isotopologues. Of the 929 labeled OBPs, 84 were unequivocally classified as direct OBPs. The remainder suggest a major contribution by indirect, hydroxyl radical induced formation of OBPs in EfOM. Overall, labelled OBPs possess a low degree of unsaturation and contributed most to OBP peak intensity – marking them as potential end products. A few direct and indirect OBPs with high peak intensity containing 18O and heteroatoms (N, S) were fragmented with CID FT-ICR-MS/MS and screened for indicative neutral losses carrying heavy oxygen. The neutral loss screening was used to detect the 18O location on the OBP and indicate the original functional group in EfOM based on known reaction mechanisms. We identified sulfoxide and sulfonic acid functional groups in selected OBPs – implying the presence of reduced sulfur in EfOM molecules – while no evidence for nitrogen containing functional groups reacting with ozone was found.

A benzo[a]phenazine-based redox species with highly reversible two-electron reaction for aqueous organic redox flow batteries

In aqueous organic redox flow batteries (AORFBs), the inherent problems, such as low energy and poor chemical stability, remain obstacles to the growth of AORFBs for the large-scale energy storage system (ESS). To address these challenges, this paper describes a novel benzo[a]phenazin-5-ol methanesulfonate (BHPS, C16H10N2O4S) containing sulfonic acid and hydroxyl functional groups, which undergoes a highly stable and reversible two-electron redox reaction in aqueous media, and allows high chemical stability, superb conductivity, high redox potential (−0.943 V) and excellent solubility. The superior chemical and electrochemical properties of the proposed BHPS are demonstrated through various experiments, including full cell-cycling tests, along with theoretical molecular analysis. Experimental results show that the BHPS with highly conductive sulfonic acid group (along with hydroxyl group) leads to 1.83 times higher kinetic constant (1.32 × 10−3 cm s − 1) and 98.07 times higher solubility (1.47 M) than the benzo[a]phenazine-5-ol (HBP, C16H10N2O). Further, the BHPS/Fe(CN)6 flow-cell cycling for 100 cycles at 60 mA cm−2 results in great coulombic and energy efficiencies of average 99.5 and 81.9%, along with dramatic charge-and-discharge capacity retention ratios of average 99.79 and 99.25% with initial charge and discharge capacities of 49.11 and 48.76 mAh, respectively. The BHPS successfully synthesized by the attachment of the sulfonic acid and hydroxyl groups to benzo[a]phenazine provides a promising anodic organic species for highly efficient AORFBs, and its performance can be further optimized by molecular engineering.

Ion rejection performances of functionalized porous graphene nanomembranes for wastewater purification: A molecular dynamics simulation study

Performances of small- and large-pore, porous graphene nanomembranes (PGNMs) (pristine and functionalized by amide, sulfonic acid, thiourea, and carbamate functional groups) for purification of heavy metal ions and nitrate-contaminated wastewater were determined using molecular dynamics (MD) simulation. At the operational conditions of the simulated membrane (150 and 0.1 MPa pressure on the left and right piston sides at 300 K), higher water flow rates were obtained in the functionalized PGNMs possessing large pores, as opposed to the non-functionalized and small-pore ones. Amide-functionalized PGNM provided the highest flow rate (380 and 330 molecules/ns for large and small pores, respectively). Cu2+ and As3+ ions were rejected at a level of 100% in the small-pore PGNMs, while the rejection level of the NO3- ions was about 95%. For large-pore PGNMs, As3+ ions were rejected at a level of 100%, while a few Cu2+ and NO3- ions could pass through the pores with no discernible dependence on the graphene surface chemistry. A radial distribution function (RDF) analysis revealed two hydration radii for all ions interacting with the surrounding water clusters. Overall, graphene surface chemistry modification did not significantly affect the ion rejection performance.

Highly efficient SWCNT/GaAs van der Waals heterojunction solar cells enhanced by Nafion doping

The atomic-level interface and strong interfacial interaction enable van der Waals (vdW) heterostructures to fabricate innovative photovoltaic devices by combing single-walled carbon nanotubes (SWCNTs) with bulk semiconductors, in which the device performance can be enhanced significantly using outstanding photoelectric property of SWCNTs. Herein, we reported a facile method to fabricate SWCNT/GaAs vdW heterojunction solar cell by transferring p-type (6,5)-enriched SWCNT film onto the n-type GaAs substrate, a power conversion efficiency (PCE) of 7.23 % has been achieved without any other treatment. Furthermore, the PCE value can be enhanced to 11.24 % by introducing Nafion as a highly effective dopant with a short-circuit current density of 24.70 mA/cm2, an open-circuit voltage of 0.64 V and a fill factor of 0.71. Our results reveal that the introduction of Nafion not only induces a stronger and closer contact at the interface between SWCNTs and GaAs, but also shows strong p-doping effect due to the existence of sulfonic acid functional groups. This p-doping effect of Nafion increases the work function of SWCNTs and subsequently enlarges the barrier height at the heterojunction for more efficient carrier separation. In addition, Nafion can also serve as an antireflection and passivation layer, reducing the incident light loss and the carrier recombination rate. These findings suggest that Nafion could be used to improve the performance of SWCNT-based vdW heterojunction devices.

Nafion/functionalized metal–organic framework composite membrane for vanadium redox flow battery

Although vanadium redox flow batteries hold great promise for energy storage systems, Nafion (being a conventional membrane material) requires improvement in terms of the crossover phenomenon. Herein, a nanoporous metal–organic framework (MOF) is applied as a membrane for vanadium redox flow batteries via addition of the MOF to a Nafion solution to prepare Nafion/MOF composite membranes via casting. Composite membranes are fabricated into a Nafion matrix by introducing small amounts of CAU-10-X (X = –OH, –CH 3 , –OS1, –OS2), an Al-based MOF synthesized with ligands having hydroxyl, methyl, and a combination of hydroxyl and sulfonic acid functional groups. The membrane physicochemical properties (such as water uptake, swelling ratio, ion exchange capacity, proton conductivity, and electrochemical properties from charge–discharge experiments on a single cell) are compared and evaluated. In 100 charge–discharge cycles of the single cell at a current density of 160 mA cm −2 , the composite membrane N/CAU-10-OS1 with 0.6 wt% dispersed MOF and a combination of hydroxyl and sulfonic acid functional groups exhibits capacity retention of 80.34% and energy efficiency of 77.56% at approximately 50 μm thickness. These values are better those achieved by commercial separation membrane Nafion 115 with 127 μm thickness tested under identical conditions and the proposed membrane is thus expected to be economically advantageous. • Using casting, Nafion/metal organic framework (N/MOF) composite membrane prepared. • Small amount of functionalized MOF in Nafion improves membrane performance in energy efficiency and cycle retention. • N/MOF membrane has lower vanadium ion permeability and thickness than Nafion 115. • N/MOF membrane shows high capacity retention (80.34%) at 100 cycles and 160 mA cm −2 .

Fabrication of a cost-effective cation exchange membrane for advanced energy storage in a decoupled alkaline-neutral electrolyte system

Herein, a cost-effective cation exchange membrane (CEM), sulfonated polyether ether ketone membrane (SPEEK-M), is prepared through heat sulfuric acid treatment followed by evaporation induced thermal phase separation. Negative charged sulfonic acid functional groups can be grafted on the polymer chains during this process. Exchange of cations, and repulsion of anions are hence realized using this membrane. To further improve the performance of the SPEEK-M, SiO2 is introduced in. It is found that ionic conductivity is increased to 46.79 mS·cm−1 for the SiO2-SPEEK-M from 19.17 mS·cm−1 for the SPEEK-M. Compared with commercial CEMs, such as DuPont N117 and Huamotech, volume expansion of the SPEEK-M is rather small after immersed in water. The membranes are then used as separators in Zn-ion hybrid capacitors (ZIHCs) with decoupled aqueous electrolytes, which includes a Zn foil anode in an alkaline electrolyte, and an activated carbon (AC) cathode in a neutral electrolyte. The electrolyte decoupling strategy maximizes the operating window of this system to 0.5 ∼ 2.2 V. The specific capacity of the AC can reach 390.0C·g−1 at a current density of 0.5 A·g−1. An energy density of 46.2 Wh·kg−1 at a power density of 3416.1 W·kg−1 can be achieved (counting the weight of AC). After gelation of the electrolytes, the growth of Zn dendrite is successfully eliminated, and capacity retention along cycling is increased to 94.3 % using the SiO2-SPEEK-M, which is better than that using the commercial DuPont N117 and Huamotech. The raw materials used here to prepare the CEMs are cheap and eco-friendly, which makes the membranes promising candidates as separators for decoupled electrolyte systems.

Directly Sulfonated Carbon Nanofibers to Improve Single-Cell Performance of Pt/CNFs–SO3H Catalyst

Due to the high cost of electrocatalysts, mass manufacturing of fuel-cell driven cars is a challenge. In the catalytic layer, the Nafion ionomer allows for minimal Pt consumption. Various carbon compounds were produced and their catalytic activities for oxygen reduction process were examined in this study. Results suggest that Pt/CNFs have the best performance due to their good electrical conductivity, rich surface defects, and the ease with which CNFs may be mass transported. As a result, CNFs were chosen to be sulfonated immediately by concentrated sulfuric acid at high temperatures. After sulfonation, the sulfonic acid functional group (–SO3H) was identified in the spectrum of Fourier transform infrared spectroscopy at a wavenumber of 1033 cm−1, and a Pt/CNFs–SO3H electrocatalyst was made using the ethylene glycol technique. After 10,000 cycles, the linear sweep voltammetry curve barely changes, and the current density can sustain 95% after 6 hours of chronoamperometric testing at 0.6 V. Pt/CNFs–SO3H can produce a maximum power density in a hydrogen/air single-cell is 397.5 mW cm−2, compared with 353.2 mW cm−2 of Pt/CNFs, a 12.5% increase, demonstrating CNFs–SO3H may significantly improve proton transportation capabilities.

Sulfonic groups functionalized Zr-metal organic framework for highly catalytic transfer hydrogenation of furfural to furfuryl alcohol

The highly selective catalytic transfer hydrogenation (CTH) of furfural (FF) to furfuryl alcohol (FOL) is a significant route of biomass valorization. Herein, a series microporous Zr-metal organic framework (Zr-MOF) functionalized by sulfonic groups are prepared. Based on the comprehensive structural characterizations by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 physisorption, Thermogravimetric (TG) and Fourier transformed infrared spectroscopy (FTIR), we find that sulfonic acid (–SO3H) functional groups are tethered on the UIO-66 without affecting the structure of the framework. Systematic characterizations (NH3-TPD, CO2-TPD, and in-situ FTIR) demonstrate that modifying of sulfonic groups on UIO-66 results in the formation of stronger Lewis acidic-basic and Brønsted acidis sites. The cooperative role of the versatile Lewis acidic-basic and Brønsted acidic sites in 60% mol fraction of sulfonic acid-containing UIO-66 (UIO-S0.6) retain high surface area and exhibit excellent catalytic performance of 94.7% FOL yield and 16.9 h−1 turnover number (TOF) under mild conditions. Kinetic experiments reveal that the activation energy of the CTH of furfural (FF) over UIO-S0.6 catalyst is as low as 50.8 kJ mol−1. Besides, the hydrogen transfer mechanism is investigated through isotope labeling experiments, exhibiting that the β-H in isopropanol is transferred to the α-C of FF by forming six-membered intermediates on the Lewis acidic-basic and Brønsted acidic sites of the UIO-S0.6, which is the rate-determining step in the formation of FOL.

Heteropolyacid supported on the composite of bentonite and ionic liquid containing acidic polymer: A highly selective catalyst for glycerol acetalization to solketal

Acetalization of glycerol that is the by-product of biodiesel to fuel additives has received considerable attention. However, formation of a mixture of products in this acid-catalysed process is a challenging issue. In this research, a highly selective catalyst is devised that can selectively acetalize glycerol to solketal. To prepare the catalyst, bentonite clay was first decorated with an acidic polymer containing sulfonic acid and carboxylic acid functional groups. Then, the carboxylic acid groups of the polymer were changed to ionic liquids through reaction with triethanolamine. Finally, phosphotungstic acid was immobilized on the bentonite-polymer composite and the resultant catalyst was characterized. To achieve the highest catalytic activity, the catalyst amount and phosphotungstic acid loading have been optimized. It was found that 10 wt.% catalyst with 20 wt.% phosphotungstic acid loading led to 100% conversion and 99% yield to solketal under solvent-free condition at 55 °C. Moreover, the catalyst could be recycled up to four reaction runs without significant loss of its activity. Comparative studies with ionic liquid-free control catalyst approved that the presence of ionic liquid in the structure of the catalyst played an important role in the selectivity of the catalyst and ionic liquid-free counterpart led to less selectivity and formation of 2,2-dimethyl-1,3-dioxane-5-ol as by-product.

Effect of TiO2 surface treatment on electron transfer in dye-sensitized solar cells

Defect states in the TiO2 nanoparticles can cause severe charge recombination and poor electron-transport efficiency when used as a photoanode in dye-sensitized solar cells (DSSCs). Herein, we report a simple and practical way to passivate the surface defects of TiO2 through hydrothermal treating with acetic acid and H2SO4, introducing a high percentage of 101 facets and sulfonic acid functional groups on the TiO2 surface. A high efficiency of 8.12% has been achieved, which is 14% higher than that of untreated TiO2 under the same condition. EIS results prove that the multiacid-treated TiO2 can promote electron transport and reduce charge recombination at the interface of the TiO2 and electrolyte. This work provides an efficient approach to engineer the electron-transport pathway in DSSCs.

Covalent organic framework with sulfonic acid functional groups for visible light-driven CO2 reduction.

In this study, a covalent organic framework (TpPa–SO3H) photocatalyst with sulfonic acid function groups was synthesized using a solvothermal method. The morphologies and structural properties of the as-prepared composites were characterized by X-ray diffraction, infrared spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, N2 adsorption–desorption measurements, and field emission scanning electron microscopy. An electrochemical workstation was used to test the photoelectric performance of the materials. The results show that TpPa–SO3H has –SO3H functional groups and high photocatalytic performance for CO2 reduction. After 4 h of visible-light irradiation, the amount of CO produced is 416.61 μmol g−1. In addition, the TpPa–SO3H photocatalyst exhibited chemical stability and reusability. After two testing cycles under visible light irradiation, the amount of CO produced decreased slightly to 415.23 and 409.15 μmol g−1. The XRD spectra of TpPa–SO3H were consistent before and after the cycles. Therefore, TpPa–SO3H exhibited good photocatalytic activity. This is because the introduction of –SO3H narrows the bandgap of TpPa–SO3H, which enhances the visible light response range and greatly promotes the separation of photogenerated electrons.